Question: $\left(5x - 1\right)\left(-8x + 1\right) = \ ?$
Answer: $= 5x \cdot \left(-8x + 1\right) - 1 \cdot \left(-8x + 1\right)$ $= \left( 5x \cdot -8x \right) + \left( 5x \cdot 1 \right) + \left( -1 \cdot -8x \right) + \left( -1 \cdot 1 \right)$ $= -40x^2 + \left( 5x \cdot 1 \right) + \left( -1 \cdot -8x \right) + \left( -1 \cdot 1 \right)$ $= -40x^2 + \left( 5x + 8x \right) + \left( -1 \cdot 1 \right)$ $= -40x^2 + 13x + \left( -1 \cdot 1 \right)$ $= -40x^2 + 13x - 1$